A basic process for the production of poly(arylene sulfide) polymers from polyhalo-substituted aromatic compounds, wherein the halogen atoms attached to ring carbon atoms react with an alkali metal sulfide in the presence of a polar organic compound at an elevated temperature, is generally known in the art. Due to a continually growing attractiveness towards thermoplastic polymeric resins, a great amount of work has been completed which resulted in the disclosure of methods for both batch and continuous operations to produce poly(arylene sulfide)s from polyhaloaromatic compounds having at least two halogen substituents per molecule. Certain processes for producing poly(arylene sulfide) resins result in a liquid reaction mixture comprising a liquid-phase polymer and a polar organic compound. In order for the polymers produced in these processes to be useful in commercial applications, the polymers must first be recovered from the reaction mixture.
One method of recovering the poly(arylene sulfide) resins from the reaction mixture is by a process referred to as the "flash recovery method". In this process the polar organic compound and some of the non-polymeric components of the reaction mixture are vaporized, leaving behind the polymer and non-volatile components. The polymer recovered by this process is generally in the form of a powdery resin. This powdery resin has, among other things, (1) proven to be difficult to filter, (2) resulted in a product that when dried is excessively dusty, (3) necessitated pelletizing the powder for extrusion purposes, and (4) resulted in other problems commonly associated with products of relatively low bulk density.
Another process used for the recovery of poly(arylene sulfide) resins from a reaction mixture is the addition of a compound functioning as a separation agent. This compound should be soluble in the reaction mixture and a nonsolvent for the polymeric resin. When certain amounts of a separation agent are used to recover the polymer from the liquid mixture, the process results in the recovery of a polymer in the form of a powder. When certain other amounts of a separation agent are used to recover the polymer from the reaction mixture, the process results in the recovery of a polymer in the form of relatively large, coarse particles.
Even though the recovery process described above can result in the formation of large polymer particles, it has been noted that the polymer still has a relatively high ash and oligomer content. The presence of ash in the polymer is undesirable since it can reduce the molding efficiency of the polymer upon injection molding applications and can also harm the electrical properties of the polymer. A relatively high oligomer content in the polymer also is disadvantageous in molding and other processing applications.
It would therefore be desirable to have a method of recovering a poly(arylene sulfide) resin from a reaction mixture which served to reduce ash and oligomer content as well as to produce large polymer particles.